1. Field of the Invention
The present invention relates to balloon catheters, and more particularly to catheters for use in centering a central support tube in a blood vessel for use in a medical treatment process.
2. Description of Related Art
Several designs of dilatation balloon catheters have been proposed in the prior art, examples of which can be seen in U.S. Pat. No. 5,160,321; U.S. Pat. No. 5,090,958; U.S. Pat. No. 4,787,388; and U.S. Pat. No. 4,581,017. Each of those balloon dilatation catheters was designed for the purpose of administering treatments to physically widen constricted blood flow passages. The term stenosis is used in this regard to refer to a region of a blood vessel which has been narrowed or constricted to such a degree that blood flow is restricted. In severe instances, treatment of the stenosis is required. Treatment of coronary blood vessels by use of the aforenoted prior art dilatation balloon catheters is referred to in the art as percutaneous transluminal coronary angioplasty (PTCA), which procedure is described in various forms in the patents identified above. The term "dilatation catheter", as used herein, will refer to the type of catheter which is principally designed for use in widening constricted blood flow passages, as is done in the PTCA procedure.
One problem associated with PTCA which has been recognized in, for example, U.S. Pat. No. 4,581,017, issued to Sahota, and U.S. Pat. No. 4,787,388, issued to Hofmann, is that, in performing the PTCA procedure, blood flow cannot be completely occluded for extended periods of time, measured in terms of well under one minute, due to the increased probability that serious damage to the patient's heart or other downstream vessels or organs will occur. The Sahota patent presents two approaches to solving this problem, a first of which is to provide a balloon catheter which, even though the inflated balloon completely occludes the blood vessel, i.e., the balloon inflates into contact with the blood vessel around the entire circumference of the blood vessel, blood is permitted to flow from a proximal side of the balloon to the distal (downstream) side of the balloon through a central lumen. The second solution proposed by Sahota, which appears to be conceptually the same as the Hofmann solution, is to design the balloon such that, when the balloon is expanded or inflated, it will not completely occlude blood flow, but which will, at the same time, provide sufficient area of balloon contact around the circumference of the blood vessel such that the tissue or other matter creating the constriction in the blood vessel can be compressed against the vessel wall in an effective manner. These designs purport to permit a longer dilatation period to be used when performing the PTCA procedure.
A further balloon catheter design of which the present inventor is aware is disclosed in U.S. Pat. No. 4,762,130, issued to Fogarty et al. This catheter was not designed as a dilatation catheter for use in performing the PTCA procedure, but instead was developed for use in removing blood clots from blood vessels, and also for use as a diagnostic tool carrying diagnostic equipment in a lumen or lumens associated with the catheter. The corkscrew shape of the balloon on this catheter was adopted specifically to avoid the application of diametrically opposed forces on the wall of the blood vessel, so as to minimize the possibility of abrasions and/or perforations occurring in the vessel wall. As such, this balloon catheter would be particularly unsuitable for use in performing the PTCA procedure or for other procedures requiring some amount of diametrically opposed force or other opposing forces to be applied.
It has previously been noted that dissection of the blood vessel is a potential problem in performing the PTCA procedure, and one or more of the aforenoted patents directed to a dilatation catheter discuss procedural steps which attempt to minimize the possibility that dissection will occur. None of the above-noted dilatation catheter patents discusses providing a balloon-type catheter having a balloon configuration which is especially well-suited for use in repairing or tacking such dissections.
It is a principal object of the present invention to provide a balloon-type catheter having features making it especially well-suited for use in processes that call for medical treatment to be administered from inside a blood vessel, and that require the treatment agent to be centered in the blood vessel to the greatest degree practicable.
It is a further principal object of the present invention to provide a balloon-type catheter in which a plurality of balloons are configured in a helical or spiral pattern extending around a central support tube or lumen, whereby a medical treatment can be administered from inside the blood vessel while preserving blood flow down the main trunk or blood vessel, and also in side branches extending from the main trunk.